Kidney stone analysis is a test done on a kidney stone to see what chemicals are in it. The test is done on a kidney stone that has been passed in the urine or removed from the urinary tract during surgery. Chemical analysis of a kidney stone shows the type of stone which can guide treatment and give information that may prevent more stones from forming. People who have had a kidney stone have a chance of having another one, so prevention measures are important.

A kidney stone (renal calculus) forms in the kidney from substances that do not pass out of the body in the urine. See a picture of a kidney stone.

A kidney stone can be as small as a grain of sand to as big as 1in. or larger. Sometimes a stone may leave the kidney and move down a ureter into the bladder. From the bladder, the stone passes through the urethra and out of the body in urine. See a picture of the urinary tract. Passing a kidney stone through a ureter or the urethra may be painless or it may cause severe pain. A kidney stone may cause other symptoms, such as blood in the urine (hematuria), pain when urinating, or a severe need to urinate.

Why It Is Done

A kidney stone analysis is done to:

• Find the chemical makeup of a kidney stone.
• Guide treatment for a kidney stone.
• Give information on how to prevent more kidney stones from forming.

How To Prepare

If you think you might have a kidney stone, talk to your doctor. He or she may have you collect the stone by straining your urine through a fine-mesh strainer or through fine gauze. Your doctor may give you a kidney stone strainer, or you may buy one from a drug store. Straining the first urine specimen of the morning is important, because a stone may pass into your bladder during the night.

Look carefully at the strainer for a kidney stone. It may look like a grain of sand or a small piece of gravel. Any stone you find should be kept dry-do not put it in fluid or urine. Put it in a cup with a lid or a plastic bag. Take it to the doctor's office or lab for analysis. Do not put tape on the kidney stone because it can change the test results.

Talk to your health professional about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?) .